Hardware requirements

AVGA has yet been successfully tested on theese devices:

ATMega88

ATMega16

ATMega168

ATMega128 (overclocked to 19.6608MHz)

ATMega644

How to connect the AVR to a monitor

The system needs one 16bit AVR timer/counter. The horizontal sync signal outputs through OCRxB of the configured timer. Vertical sync output port
and pin can be set in config_hw.h. Pixel stream appears at high nibble of a configured port.

The pixel stream can be converted using resistor video DAC to RGB compounds with standard 16 color EGA/VGA pallette.

Where R1=R2=R3, R4=R5=R6 and R7=R8=R9;
By adjusting R1:R4 ratio, contrast between lower and upper color page is changed easily. I suggest range from 2:3 to 1:2.
Actual resistor values depends on monitor's input levels and impedance.
Here are some examples: